Abstract:

Sixty-five endophytic bacteria strains were isolated from healthy blueberry fruits. Antagonistic bacterium strain YJ15 was screened with the agar plate diffusion method，and identified as Bacillus siamensis based on the morphological，physiological and biochemical characteristics，and 16S rRNA sequence analysis. Based on single factor tests，three important factors of temperature，pH and nitrogen source were screened by Plackett-Burman experimental design. The optimal fermentation conditions for glucose 20 g · L-1，yeast powder 36.01 g · L-1，FeSO4 1.5 g · L-1，glycerol 1 g · L-1，K2HPO4 1.5 g · L-1，inoculation amount 1 mL，rotational speed 150 r · min-1，temperature 31.35 ℃，pH 7.43 and cultural time 15 hours were determined by steepest ascent experiment and response surface methodology. The antifungal effects of fermentation broth of strain YJ15 on nine pathogenic fungi were obvious with the inhibition rate of 43.42%–92.39%. The fermentation broth of strain YJ15 with lower disease incidence and lesion diameter had better control effects with no significant difference compared with that of carbendazim，and could be useful to effectively control Botrytis cinerea causing blueberry gray mold.

Key words: blueberry gray mold, antagonistic bacterium, identification, fermentation condition, control effect